Creating an African-style keyhole garden

The Keyhole Garden concept is brilliantly simple. A circular raised bed has a centre compost basket that distributes nutrients to the surrounding lasagne-style garden bed. A small pie-slice section of the bed is used for easy access to the centre compost basket forming the keyhole design.

Kitchen and garden waste, along with household grey water, are added to the centre basket. The soil bed layers are slightly sloped away from the centre to aid water and “compost tea” distribution. As the materials decompose, soil, composting materials and amendments are added to the bed in later growing seasons.

Keyhole Garden Construction

Compost Basket: A tube, 1′ to 1-1/2′ (.5 meters) in diameter and tall enough to extend well above the centre of the bed, can be fashioned from anything that will allow water to pass through into the surrounding bed like chicken wire, fencing, or sticks. We are using wire.

Outer Border Walls: Anything that will contain the soil could be used: stones, bricks, or blocks can be stacked into place; boards or branches could be driven into the ground; sand bags or old tires could work as well. We are using bricks.

Planting Bed Fill: Use the same materials as for a lasagne garden, or compost pile, such as cardboard, paper, manure, leaves, straw, hay, old potting mix, or wood ashes, then finish the surface for planting with top soil.

Layout:

A cleared level area 2.8 meters in diameter for this Keyhole Garden.

The cut out area of the keyhole should be wide enough to allow easy access to the compost basket when adding materials, removing compost, or making basket repairs if needed. Positioning the cut out on the South side of the circular garden would use the dark space of the bed that would not receive full sun, thus leaving all the sunny sides for planting.

All the layers added to the bed should slope downward to the outer border wall. The slope helps direct moisture from the compost basket out into the bed.

The outer border wall can be as high as needed for the comfort of the gardener and the amount of sourced materials. The top surface of soil should stay below the outer walls to contain rainwater and prevent the soil from running off.

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About Permablitz Melbourne

Welcome to Permablitz Melbourne - where we get together and have fun learning about, designing and implementing suburban permaculture systems. Our focus is edible gardens, and our ultimate aim is to make the suburbs edible enough such that should food become unaffordable, we don’t even notice.